FAA ATPL test: CG shift in index arms
I'm stuck here with these W&B questions. I figured out the MAC part, but on the index arms I'm completly confused, since there is no real explanation in the theory book:
Q:
Where is the new CG if the weight is shifted from the forward to the aft compartment under Loading Condition WS-5?
A:
-97.92, +19.15, +13.93 index arm.
The theory book only gives you the explanation:
CG (index arm) = CG (inches of the Datum) - 580
The table is the good old one from DC-9:
Loaded weight 88 300 lbs
Loaded MAC 25.5%
Weight Change 3300 lbs
Fwd Comp centroid -227.9 Index arms
Aft Comp centroid +144.9 Index arms
Lemac -30.87 Index arms
Does anyone have a how to do?
Many thanks
Dani